With the internal combustion engines customary at the moment with pairwise balance shafts, a unit containing both balance shafts is connected to the crankshaft bearing from below. This has the advantage of being able to equip conventional basic engines with balance shafts without any greater construction interventions, but does increase the construction height of the engine. This is undesirable with sloping engine hoods. In the completely new design of an internal combustion engine, one therefore endeavors to integrate the balance shafts into the engine, to integrate them at the side into or onto the crankcase or the engine block (which are anyway usually integral).
What causes problems here is the installation and the drive of the balance shaft unit. It is known from DE-A-29 35 384 to support a balance shaft at the side in a cover and to drive it by means of a chain. A drive without clearance is possible thanks to a chain tensioner, but the chain makes the installation a lot more difficult.
If a balance shaft is driven by means of gears, the load case typical for balance shafts (small, but pulsing transmitted torque at a very high rotational speed) requires special measures to avoid irritating noises. A proven measure is the reduction in the tooth clearance, in particular of the rotational flank clearance, which requires a very precise setting of the shaft position. It is known from EP-B-916 833 for balance shafts with gear drive arranged pairwise beneath the crankshaft to set the whole balance shaft unit by means of rotatable eccentrics.